I made this fan card (twice!) for Mother's Day. Technically it's not a pop up card, but a mechanical card in which the fan opens as the top tab is pulled. Pulling on the bottom tab closes the card. Ingenious!
Even with the help of my trusty Craft Robo, I pretty much spent one whole day, on and off, making and arranging the flowers. Which, by the way, were inspired by a gorgeous illustration by DaPino.
There is a fan card how-to in Making Mechanical Cards by Sheila Sturrock. I highly recommend this book if you are interested in mechanical cards. The author drew upon a collection of Victorian and Edwardian greeting cards, creating templates for 25 designs from that era.
Extreme Cards and Papercrafting: pop up cards, movable cards, digital crafts and unusual papercrafts.